Method of timed shift to neutral in apparent stationary modes

ABSTRACT

A control for a transmission and a clutch monitors conditions to determine when a vehicle associated with the clutch and transmission is likely in a stationary state. If the vehicle appears to be stationary, with the transmission engaged and the clutch open, then the control determines that the transmission should be moved to a neutral position. Upon movement to the neutral position, the control then closes the clutch. It is preferable for a vehicle remaining stationary to have its clutch closed and its transmission in neutral than to have its transmission engaged and its clutch open. In a further aspect of this invention, the neutral state is verified by testing the ability to move one of the transmission shift components. If the transmission shift component can move beyond a predetermined amount, this is indicative that the transmission is in neutral.

RELATED APPLICATIONS

This application is a divisional of Ser. No. 10/701,791, which was filedNov. 5, 2003.

BACKGROUND OF THE INVENTION

This invention relates to a shift of a heavy vehicle transmission intoneutral, when conditions indicate that the vehicle has remainedstationary for a period of time.

Further, many modem transmissions are associated with an automatedclutch. An automated clutch is also actuated by an actuator.

Heavy vehicles have typically been provided with an automated clutch andan automatic, automated, or manual transmission. In an automatic orautomated transmission, some actuators are provided with thetransmission to move a transmission shift apparatus between the variousspeed ratios. Thus, as is known, an actuator such as a fluid piston willmove shift forks, etc., to disengage a gear, and then move to engageanother gear when a transmission speed ratio change is beingimplemented.

One concern with modern heavy vehicles occurs when a vehicle is toremain stationary for a period of time. A driver may sometimes open theclutch, and leave the transmission engaged, while the vehicle continuesto run. For several reasons, it would be desirable for the transmissionto be in neutral and the clutch closed during these stationary runningperiods. However, to date, a control to achieve this desired state hasnot been developed.

SUMMARY OF THE INVENTION

In the disclosed embodiment of this invention, a control monitorsoperation of a heavy vehicle transmission and clutch. If the clutch isopen, but conditions indicate the vehicle has remained stationary for aperiod of time, then the control may power the system to move thetransmission into a neutral state. When a neutral state has beenverified, the clutch is closed. Now, the vehicle remains stationary withthe clutch closed and the transmission in neutral.

In preferred embodiments of this invention, the conditions that could besensed included zero or low vehicle speed, with a running engine,transmission in gear, and no shift lever, brake pedal or acceleratorpedal movements. Changes in any one of these conditions could restart atimer. However, once a particular period of time has expired with theseconditions being within the indicated state, then a decision may he madethat the vehicle is stationary. At that time, the control may actuatethe shift actuator to move the transmission to neutral.

In a preferred embodiment, prior to this automatic shift to neutral,some buzzer or other warning may be utilized to signal the decision tomove to neutral. In this way, the driver would not be surprised by theaction should he still be in the vehicle. Also, an indicator light orwarning sound could advise the operator to implement a neutral shift. Ifthe operator does not address the problem, then the automatic shift mayoccur.

Further, after shifting to neutral, but prior to closing the clutch,some reliable way of ensuring the neutral state is preferably utilizedIn one disclosed in this invention, the select actuator, a part of thetransmission shift apparatus that selects a particular shift rail, isutilized to ensure a neutral state. In particular, the select actuatoris moved in a first direction, and a sensor senses the amount ofmovement. The actuator is then moved in the opposed direction, andagain, the amount of movement is sensed. An absolute difference betweenthe two values is taken. If the absolute value is above a predeterminedamount, the control can determine that the vehicle is in neutral. Statedin a simpler manner, the select actuator is not movable for anysignificant difference when a transmission gear is engaged. Thus, if theselect actuator is movable a significant difference when moved in thesetwo directions, this would be a reliable indication that thetransmission is in neutral.

If this verification fails to indicate a neutral state, then the systemmay attempt to drive the transmission to neutral again.

These and other features of the present invention can be best understoodfrom the following specification and drawings, the following of which isa brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system to incorporate this invention.

FIG. 2 is a flow chart.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows a vehicle driveline 20 incorporating an engine 22 driving aclutch 24. Clutch 24 is selectively engaged to transmit drive from theengine 22 into a transmission 26. As shown, the transmission 26 is ofthe type provided by an actuator box 28 such that transmission gearshifts can be achieved without manual movement by the operator. As shownschematically, and as known, a shift collar 30 may be movable in a pairof distinct directions to selectively engage one of a pair of gears 32.The transmission is shown schematically, and such automatedtransmissions are known in the art. The present invention is directed totransmissions wherein an actuator 28 is operable to engage or disengageparticular transmission gear speeds. Such actuators are incorporatedinto automated or automatic transmissions.

A portion of the shift apparatus, and namely the select actuator 34 isalso shown schematically in this view. An actuator piston 36, which ispart of actuator 28, is operable to rock the select actuator 34 betweentwo positions to achieve a particular shift rail position, again asknown. If the transmission is not in neutral, that is to say a gear isengaged, the select actuator 34 is not typically movable any appreciabledistance. Thus, if the select actuator is movable for a significantdistance, as measured by sensors 37, then an indication can be made thatthe transmission is in neutral.

A control 40 takes advantage of this fact to verify neutral in apreferred embodiment by actuating the actuator piston 36 to rock theselect actuator 34 between two positions. The extent of movement issensed by the sensors 37, shown schematically. If the magnitude ofmovement between the two positions exceeds a predetermined amount, thena determination can be made that the transmission 26 is in a neutralstate.

As also shown in FIG. 1, a shift lever 38 may be operated by theoperator to request a transmission gear ratio change. Signals from eachof the main components described above are all sent to the control 40,shown schematically.

The present invention includes the control 40 monitoring operationalconditions. A flow chart is shown in FIG. 2. If the control 40determines that the vehicle is likely in a stationary state, with thetransmission engaged and the clutch open, then the control 40 will powera shift to neutral. Among the conditions the control 40 may look todetermine this mode will be a vehicle speed below a predeterminedmaximum, the engine running, the transmission engaged in gear, and noshift lever, brake pedal or accelerator pedal movements. If suchconditions exist for a predetermined period of time, then thetransmission control 40 may move to step 52 and order a shift to neutralby the actuator 28. However, should any one of the conditions mentionedabove change during the particular time period, then the control willrestart a timer.

Once the transmission actuator 28 has moved the shift actuator 30 suchthat the transmission is in neutral, verification of the neutralcondition is performed. In particular, and in the preferred embodiment,the select actuator 34 is moved between two sides. If the amount ofmovement sensed by the sensors 37 is significant, or above apredetermined amount, then a decision can be made that the transmissionis in neutral. The select actuator 34 would typically not be movable anyappreciable distance if the transmission were nor in neutral. Thus, thedetermination of significant movement can be taken as verification thatthe transmission is in neutral. Once it is determined or verified thatthe transmission is in neutral, the clutch 24 may be closed.

An operator display 100 or warning may provide the operator with asignal that the shift to neutral is about to occur. Also, once thedetermination has been made that the transmission should be in neutral,the display 100 may provide a prompt to the operator such as a flashinglight, or some indication that the driver should himself move thetransmission to neutral if the driver does not follow this prompt, thenthe transmission may then move to the automatic shift to neutral.

If in fact the verification fails to indicate the transmission is inneutral, the system may return to method box 52 and again attempt toshift to neutral. Alternatively, the unit may be shifted back to fullyengaged before a retry.

Although a preferred embodiment of this invention has been disclosed, aworker of ordinary skill in this art would recognize that certainmodifications would come within the scope of this invention. For thatreason, the following claims should be studied to determine the truescope and content of this invention.

1.-7. (canceled)
 8. A method of ensuring a transmission is in a neutralposition comprising the steps of: (1) providing a transmission shiftassembly including movable components which are movable to move gearswithin a transmission; (2) moving one of said movable components, andsensing a magnitude of movement of said one of said movable components,and comparing said magnitude of movement to a predetermined amount; and(3) verifying the said transmission is in a neutral position if saidmagnitude of movement is above a predetermined amount.
 9. A method asset forth in claim 8, wherein said one of said movable components is aselect actuator for said transmission.
 10. A vehicle transmission andclutch control comprising: a vehicle clutch selectively opened andclosed to drive a transmission, said transmission being provided with anactuator for moving shift components to selectively engage and disengagea plurality of gears, and said vehicle clutch being powered betweenopened and closed positions, and a control for controlling said actuatorand said vehicle clutch; said control being provided with signalsindicative of a plurality of monitored conditions, said control startinga timer should said plurality of monitored conditions indicate that avehicle associated with said vehicle clutch and said transmission isstationary with said transmission engaged; and said control beingoperable to move said transmission to a neutral state if said timerexceeds a predetermined amount with said plurality of monitoredconditions still indicating the vehicle is stationary.
 11. A vehicletransmission and clutch control as set forth in claim 10, wherein saidcontrol further provides a signal to prompt an operator to move thetransmission into neutral if said plurality of monitored conditionsindicate that the vehicle is stationary and the transmission is engaged.12.-16. (canceled)